1. Field of the Invention
The present invention generally relates to a sheet processing apparatus to bind together a bundle of sheets and an image forming system including the sheet processing apparatus and an image forming apparatus, such as a copier, a facsimile machine, a printer, or multifunction machine capable of at least two of these functions.
2. Description of the Background Art
There are sheet processing apparatuses, so-called finishers or post-processing apparatuses, that align a bundle of sheets (hereinafter “a sheet bundle”) output from an image forming apparatus and bind the sheet bundle with metal staples. Such sheet processing apparatuses can automatically staple a number of sheet bundles on which images are formed and are widely used for convenience and efficiency thereof.
From the viewpoint of environmental preservation, it is desirable to recycle printed paper. To recycle sheet bundles bound with staples such as those made of metal, it is necessary to remove and separate the staples from paper. Thus, it is not convenient. Additionally, the removed staples are wasted.
By contrast, there are hand-held staplers, so-called staple guns or powered staplers, capable of binding sheets without staples. For example, JP-S36-13206-Y discloses a hand-held stapler capable of clamp binding, and JP-S37-7208-Y discloses a hand-held stapler that makes cut holes in sheets, bends cut portions, and inserts the cut portions into the cut holes.
There are hand-held staplers that press (that is, emboss) multiple sheets with a pair of tooth forms, causing fibers of the sheets to tangle with each other, and thereby tie the sheets together. Alternatively, sheets are bound together using other types of processing such as half blanking, lancing, bending, and inserting. Sheets bundles free of staples can be directly put through a shredder. Thus, such binding tools can reduce consumption of consumables, make recycling easier, and be effective to save resources.
For example, JP-2010-184769-A proposes a sheet binding device that involves embossing and binds sheets according to the thickness of the sheet bundle with a simple configuration. Specifically, the sheet binding device forms projections and recesses in the direction of the thickness of a sheet bundle using a pair of tooth forms, thereby binding the sheet bundle. The pair of tooth forms is movable in the thickness direction of the sheet bundle and configured to clamp the sheet bundle to form the projections and the recesses in the thickness direction. During embossing, the interval between the tooth forms in the thickness direction of the sheet bundle is changed according to the thickness of the sheet bundle.